A: What is the largest animal living on the land?
B: It’s the elephant.
A: The smallest animal?
B: Plankton（浮游动物）is the smallest animal in the world. It is a single cell organism（单细胞生物）.
A: Then what animal is the tallest?
B: Giraffe have the longest neck, so they should be the tallest one on the earth.
A: Which is the biggest and smallest among the various kinds of bird?
B: The biggest is the ostrich（鸵鸟）, which can up to 2.75 meters tall, and 2 meters long. The smallest is called the hummer（蜂鸟）.
A: We know that there are much more pets in our lives. Do you know the smallest dog?
B: Sorry, I really don’t know this. Can you tell me?
A: Sure, the smallest dog is called Danka（吉娃娃狗）, just 18.8 cm long.
B: Yeah, it’s so amazing! What a supernatural（神奇）world!